Mobile and wireless communications are exhibiting explosive growth-evident by the continued growth of cellular systems, 802.11-based data communications and the increased demand for broadband-based communications. The Internet's success results from IP architecture's robustness, flexibility, and ability to scale over multiple wired networks. The Internet is in the process of expanding to wireless and ad-hoc networking environments. Wireless environments will be able to support mobility—a feature that is desired by the highly dynamic user community. One of the main constraints limiting the spread of wireless networking is that systems supporting mobile communications have considerably less transmission capacity than wire-based networks. This invention introduces a novel wireless communications and antenna design in order to significantly increase the number of users that systems can support, and increase wireless networks' aggregate transmission capacities.
The field of the invention is antenna system design for wireless data networks, by dividing three-dimensional space into multiple regions or sectors, wherein the antenna system design primarily occupies one sector of the space. Consequently, it is possible to use the same frequency at the same time in non-interfering parts of three-dimensional space. A similar concept of sectoring has been used in cellular-based systems, however this invention uses a different approach by which the sectoring, the specific antenna structure and the channel selection process is done dynamically (packet-by-packet) both in an access point and a mobile device. Energy can then be channeled to the antenna module, which will maximize communication efficiency, and reduce power requirements that are important for mobile users who don't have fixed power sources.
The field of the invention further relates to smart antenna design, e.g.: phased array antennas, SDMA (space division multiple access) antennas, spatial processing antennas, digital beam-forming antennas, ceramic antennas, strip antennas, adaptive antenna systems, flat panel antennas, etc. Smart antenna systems can be characterized as either switched-beam or beam-forming systems, with the following distinctions regarding the choices in transmission strategy:                Switched-beam antenna systems form multiple fixed-beams with heightened sensitivity in predefined directions. These antenna systems detect signal strength, choose from one of several predetermined fixed-beams, and switch from one beam to another as the mobile moves throughout the sector. Instead of shaping the directional antenna pattern with the metallic properties and physical design of a single element (e.g., a sectorized antenna), switched-beam systems combine the outputs of multiple antennas in such a way as to form finely sectorized (directional) beams with more spatial selectivity than can be achieved with conventional, single-element approaches.        Beam-forming antennas have an infinite number of patterns that are adjusted in real-time. Using a variety of signal-processing algorithms, the adaptive system takes advantage of its ability to effectively locate and track various types of signals to dynamically minimize interference and maximize intended signal reception.        
Both switched-beam antennas and beam-forming antennas attempt to increase gain and minimize interfering signals according to the location of the individual user. The system and antenna designs in this invention are aimed at increasing gain, reducing power requirements and minimizing interfering signals with respect to a large number of mobile users who are concurrently and continuously tracking and communicating with their respective access points.
In addition to these techniques, smart antennas provide a new method of multiple access to the users, which is known as space division multiple access (SDMA). The SDMA scheme, sometimes referred to as space diversity, uses smart antennas to provide control of space by providing virtual channels in an angle domain. With the use of this approach, simultaneous calls in various different cells can be established at the same carrier frequency. SDMA complements CDMA (code division multiple access) and TDMA (time division multiple access) by increasing the number of users that can access an existing wireless phone or data system by exploiting the spatial characteristics of the channel itself through highly developed implementation of an intelligent antenna system's capabilities for receiving and transmitting.
SDMA antenna systems are used on board various satellite systems. SDMA permits multiple signals of different polarization to simultaneously access the same satellite transponder. Users share a common frequency, but are separated by spatial processing. With SDMA, satellites may achieve signal separation by using beams with horizontal, vertical or circular polarization. This technique allows multiple beams to cover the same earth surface areas. Additionally, the satellite could achieve spatial separation by using separate antennas or a single antenna with multiple beams.
The following is a list of a prior art and background references that are relevant and are used as the foundation of this invention: [T. S. Rappaport, Wireless Communications: Principles & Practice, Prentice Hall, Upper Saddle River, N.J., 1999]; [J. C. Liberti and T. S. Rappaport, Smart Antennas for Wireless Communications: IS-95 and Third-Generation CDMA, Prentice Hall, N.J., USA. 1999, ISBN 0-13-719287-8]; [IEEE 802.11—wireless LAN (local area network)]; [IEEE Std 802.16-2001, Part 16: Air Interface for Fixed Broadband Wireless Access Systems]; [IEEE Std 802.15.1-2002, Part 15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Wireless Personal Area Networks (WPANs)]. Specific antenna design considerations are taught in [Understanding Antennas for Radar Communications and Avionics (Van Nostrand Reinhold Electrical/Computer Science and Engineering Series) by Benjamin Rulf, Gregory A. Robertshaw (Contributor); 335 pages; Kluwer Academic Publishers; May 1987, ISBN: 0442277725]. Various issues that are related to radio propagation of mobile cellular system are discussed in [Bertoni, H. L., “Radio Propagation for Modern Wireless Systems”, Prentice Hall, ISBN 0130263737, 2000].
The two articles [LAL C. GODARA, “Applications of Antenna Arrays to Mobile Communications, Part I: Performance Improvement, Feasibility, and System Considerations,” PROCEEDINGS OF THE IEEE, VOL. 85, NO. 7, JULY 1997, pp. 1031-1060; and LAL C. GODARA, “Applications of Antenna Arrays to Mobile Communications, Part II: Beam-Forming and Direction-of-Arrival Considerations,” PROCEEDINGS OF THE IEEE, VOL. 85, NO. 8, AUGUST 1997, pp. 1195-1245] and the extensive list of references therein covers many of the current antenna designs for mobile communications. The following two articles further cover issues related to smart antennas and space division multiple access: [Martin Cooper and Marc Goldburg, “Intelligent Antennas: Spatial Division Multiple Access,” 1996 ANNUAL REVIEW OF COMMUNICATIONS, pp. 999-1002; and M. Cooper, Antennas get Smart, Scientific American, July 2003, pp. 48-55].
Prior Art:
The following examines related patents to this current patent application. The invention describes in [“Direction-agile antenna system for wireless communications,” U.S. Pat. No. 6,486,832, Abramov, et al., Nov. 26, 2002] discloses an antenna steered by an electro-mechanical device in the direction that ensures maximal quality of the incoming signal.
The invention described in [“AI antenna driving device and method for controlling the same,” U.S. Pat. No. 6,278,405, Ha, et al., Aug. 21, 2001] tries to overcome the limitations of a fixed antenna by using a mechanical antenna steering mechanism to improve reception and transmission.
The invention described in [“Multiple antenna cellular network,” U.S. Pat. No. 6,070,071, Chavez, et al., May 30, 2000; “Multiple antenna cellular network,” U.S. Pat. No. 6,078,823, Chavez, et al., Jun. 20, 2000] concentrates on cellular communication networks. It proposes a multiple antenna cellular network communicates with a mobile station over a plurality of antennas. The antennas are arranged in a plurality of positions to customize a cell or cells. A transceiver is coupled to the antennas and configured to receive inbound information from the mobile station and transmit outbound information to the mobile station. A processor is coupled to the transceiver and configured to decode the inbound information and to encode the outbound information to communicate with the mobile station. In another embodiment, the antennas are similarly deployed to create a cell or cells. The transmit signal power is continuously modified to improve quality and to move the nulls so that a fixed location user can receive a high quality signal. A cell can be served by multiple antennas overcoming the limitations imposed by conventional cellular systems. Communications are supported through walls, ceilings, floors and buildings to reduce interference, improve performance and improve quality of service.
Exemplary embodiments are provided for use with the Global Systems for Mobile Communication (GSM) protocol and can be applied to other digital technologies. The invention described in [“Switched directional antenna for automotive radio receivers,” U.S. Pat. No. 6,449,469, Miyahara Sep. 10, 2002] proposes a method for improving communications from and to a moving vehicle. It relates, in general, to a mobile radio receiver with reduced distortion and reduced signal fading, and more specifically, to a switched directional antenna utilizing predetermined antenna patterns aligned with the front, hack, left and right sides of a mobile vehicle. A primary source of noise and distortion in radio receivers is derived from multi-path interference. This is a localized effect resulting from interaction between separate signals from a transmitter, which traverse different paths (e.g., via reflections) to reach a receiving antenna. Because of the superposition of several signals (e.g., echoes and direct waves), the signal strength of the received signal changes drastically and may fall below the noise floor. Based upon the differences in path lengths of each received wave, the multi-path distortion or fading may include short—time delayed multi-path interference and/or long—time delayed multi-path interference signals.
A well-known means for reducing multi-path distortion is through use of space-diversity antennas in a radio receiver system. By switching between antenna signals from spaced apart antennas. Specific multi-path events can be avoided if the antenna spacing is enough to insure that both antennas will not experience the same multi-path event at the same time. By using the different antennas placed on the vehicle it is possible to reduce the multi-path effect and improve the communication system performance.
The invention described in [“Multi-sector pivotal antenna system and Method,” U.S. Pat. No. 5,969,689, Martek, et al., Oct. 19, 1999] proposes using an omni-directional coverage multi-beam antenna composed of facets or antenna modules that comprise a regular polygon of n sides inscribed in a circle of radius r which defines an adjustable composite conical surface. The antenna modules are independent antenna arrays creating an independent beam. One advantage of such a system is that the radiated wave front associated with such antenna modules is always substantially broadside to the array resulting in limited scan loss effects. Furthermore, the independence of the disclosed antenna modules is important as it allows each module's beam to be either electrically or mechanically steered to affect elevation or directional beam control. The individual antenna modules can be steered to be directed within the area covered by a module to optimize communications capability.